Overview. Caffeine is a chemical primarily found in coffee and tea, but which also appears in various sodas, sports drinks and foods. It is a stimulant, therefore causing changes in metabolism as well as increases in focus and energy. Caffeine is addictive and can cause withdrawal following cessation after frequent use.
robot. 1  a machine that resembles a human and does mechanical, routine tasks on command. 2  a person who acts and responds in a mechanical, routine manner, usually subject to another's will; automaton. 3  any machine or mechanical device that operates automatically with humanlike skill.
A machine is a tool containing one or more parts that uses energy to perform an intended action. Machines are usually powered by mechanical, chemical, thermal, or electrical means, and are often motorized. Historically, a power tool also required moving parts to classify as a machine.